Sealed compressor and refrigeration device

ABSTRACT

A sealed compressor includes sealed container that contains electric element, and compression element driven by electric element. Compression element includes shaft that includes main shaft portion, and eccentric shaft portion integrally movable with main shaft portion, and bearing portion that supports main shaft portion of shaft to constitute a cantilever bearing. Compression element further includes cylinder that compresses gas, piston reciprocatively inserted into cylinder, and connecting rod that connects eccentric shaft portion with piston.

TECHNICAL FIELD

The present invention relates to a sealed compressor capable of reducing sliding loss of a piston, and a refrigeration device including this sealed compressor.

BACKGROUND ART

There has been a recent demand for higher efficiency of a sealed compressor included in a refrigerator or other refrigeration devices with an aim to reduce power consumption.

A type of sealed compressors developed under these circumstances decreases distortion of a reciprocating piston produced within a compression chamber during a compression stroke to reduce sliding loss and improve efficiency (for example, see PTL 1).

A conventional sealed compressor is hereinafter described with reference to the drawings. FIG. 8 is a longitudinal cross-sectional view of a conventional sealed compressor. FIG. 9 is a cross-sectional view illustrating a main part around a piston of the conventional sealed compressor during a compression stroke. FIG. 10 is a cross-sectional view illustrating the main part around the piston of the conventional sealed compressor during a suction stroke.

As illustrated in FIGS. 8 through 10, sealed container 301 of the conventional sealed compressor contains electric element 304 including stator 302 and rotor 303, and compression element 305 driven by electric element 304. Shaft 310 includes main shaft portion 311, and eccentric shaft portion 312 eccentrically disposed at one end of main shaft portion 311. Rotor 303 is fixed to main shaft portion 311.

Cylinder block 314 includes substantially cylindrical cylinder 315, and bearing portion 320. Piston 323 is reciprocatively inserted into cylinder 315. Valve plate 350 is attached to an end surface of cylinder 315. Cylinder 315 and piston 323 constitute compression chamber 316.

As illustrated in FIG. 9, piston pin 325 attached to piston 323 is positioned in parallel with eccentric shaft portion 312. Bearing portion 320 supporting main shaft portion 311 of shaft 310 constitutes a cantilever bearing.

Connecting rod 326 is composed of large-hole end portion 328, small-hole end portion 329, and rod portion 330. Large-hole end portion 328 engages with eccentric shaft portion 312. Small-hole end portion 329 connects with piston 323 via piston pin 325. Eccentric shaft portion 312 and piston 323 connect with each other via connecting rod 326 and piston pin 325.

In the drawing, shaft center C indicates a shaft center of piston 323, while shaft center D indicates a shaft center of cylinder 315.

Operation of the conventional sealed compressor thus constructed is hereinafter described. When electric element 304 is turned on, rotor 303 causes rotation of shaft 310. Rotational movement of eccentric shaft portion 312 produced in accordance with rotation of shaft 310 is transmitted to piston 323 via connecting rod 326. As a result, piston 323 starts reciprocating movement within cylinder 315. This reciprocating movement of piston 323 sucks refrigerant gas from a cooling system (not shown) having a freezing cycle, and supplies the refrigerant gas into compression chamber 316. The refrigerant gas is compressed in compression chamber 316, and again discharged to the cooling system.

During a compression stroke of the reciprocating movement of piston 323, piston 323 is pressed toward eccentric shaft portion 312 by a compression load applied to compress the refrigerant gas. As a result, shaft 310 is tilted within bearing portion 320. In this case, shaft center C of piston 323 is also tilted in accordance with the tilt of shaft 310. Accordingly, for alignment between shaft center C of piston 323 and shaft center D of cylinder 315 during the compression stroke, shaft center D of cylinder 315 is disposed in a tilted position in correspondence with the tilt of shaft center C of piston 323. This structure decreases distortion of piston 323 within cylinder 315 during the compression stroke, thereby reducing sliding loss to achieve higher efficiency.

In the conventional sealed compressor, however, piston 323 is pulled toward cylinder 315 by a suction load applied to suck refrigerant gas during a suction stroke of the reciprocating movement of piston 323 as illustrated in FIG. 10. In this case, shaft 310 is tilted toward cylinder 315. As a result, shaft center C of piston 323 deviates from shaft center D of cylinder 315 disposed in a tilted position beforehand. Particularly when the suction load increases under severe driving conditions including a high compression ratio, shaft center C of piston 323 is further tilted in such a manner as to press a tip end of piston 323 against a bottom of compression chamber 316. This condition produces distortion of piston 323, and increases input accordingly.

CITATION LIST Patent Literature

PTL 1: Japanese Translation of PCT Publication No. 2011-508840

SUMMARY OF THE INVENTION

The present invention solves the aforementioned conventional problems by providing a highly efficient sealed compressor capable of preventing input increase by reducing distortion produced by a tilt of a piston during a suction stroke.

A sealed compressor according to the present invention includes a sealed container that contains an electric element, and a compression element driven by the electric element. The compression element includes a shaft that includes a main shaft portion, and an eccentric shaft portion integrally movable with the main shaft portion, and further includes a bearing portion that supports the main shaft portion of the shaft to constitute a cantilever bearing. The compression element further includes a cylinder that compresses gas, a piston reciprocatively inserted into the cylinder, and a connecting rod that connects the eccentric shaft portion with the piston. An angle a1 formed by a first center line indicating a shaft center of the bearing portion, and a second center line indicating a shaft center of the cylinder, and an absolute value c1 of an angle of a tilt of the shaft with respect to the bearing portion satisfy equation (1). An outer circumferential surface of the piston includes a seal portion producing a clearance from an inner circumferential surface of the cylinder, and forming a sliding surface, an extension portion disposed in a rear of the seal portion, and forming a sliding surface, and a non-sliding portion disposed in the rear of the seal portion, and not forming a sliding surface.

a1=π/2+c2  (1)

In this structure, a side extension portion constituting a sliding surface is disposed in the rear of the seal portion forming a sliding surface of the piston even in a state of large deviation between the shaft center of the cylinder and the shaft center of the piston during a suction stroke. This structure eliminates a sliding surface in the vertical up-down direction. Accordingly, local distortion of the piston in the vertical up-down direction decreases at the time of a tilt of the piston.

The sealed compressor according to the present invention reduces local distortion produced during a suction stroke of a piston for prevention of input increase, thereby improving efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a sealed compressor according to a first exemplary embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the sealed compressor according to the first exemplary embodiment of the present invention when a compression load is applied during a compression stroke.

FIG. 3 is an enlarged cross-sectional view of the main part of the sealed compressor according to the first exemplary embodiment of the present invention when a suction load is applied during a suction stroke.

FIG. 4 is a cross-sectional view of a cylinder and a piston, as viewed from above, of the sealed compressor according to the first exemplary embodiment of the present invention.

FIG. 5 is a longitudinal cross-sectional view of the cylinder and the piston of the sealed compressor according to the first exemplary embodiment of the present invention.

FIG. 6 is a cross-sectional view of a main part illustrating a positional relationship between a bearing portion and the cylinder of the sealed compressor according to the first exemplary embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of a refrigerator according to a second exemplary embodiment of the present invention.

FIG. 8 is a longitudinal cross-sectional view of a conventional sealed compressor.

FIG. 9 is a cross-sectional view of a main part around a piston during a compression stroke of the conventional sealed compressor.

FIG. 10 is a cross-sectional view of the main part around the piston during a suction stroke of the conventional sealed compressor.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments according to the present invention are hereinafter described with reference to the drawings. The present invention is not limited to the exemplary embodiments presented herein.

First Exemplary Embodiment

FIG. 1 is a longitudinal cross-sectional view of a sealed compressor according to a first exemplary embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the sealed compressor when a compression load is applied during a compression stroke. FIG. 3 is an enlarged cross-sectional view of the main part of the sealed compressor when a suction load is applied during a suction stroke. FIG. 4 is a cross-sectional view of a cylinder and a piston, as viewed from above, of the sealed compressor. FIG. 5 is a longitudinal cross-sectional view of the cylinder and the piston of the sealed compressor. FIG. 6 is a cross-sectional view of a main part illustrating a positional relationship between a bearing portion and the cylinder of the sealed compressor.

As illustrated in FIGS. 1 through 6, sealed container 101 contains electric element 104 including stator 102 and rotor 103, and compression element 105 driven by electric element 104. Lubricant 106 is stored in an inner bottom of sealed container 101.

An interior of sealed container 101 is filled with hydrocarbon type R600a refrigerant 106. Lubricant 102 that is low-viscosity oil in a range from VG3 to VG10 is sealed into the bottom of sealed container 101.

Electric element 104 includes rotor 103 and stator 102, and is driven by an inverter (not shown) at a plurality of driving frequencies including at least a driving frequency equal to or higher than a power supply frequency. A maximum driving frequency for driving electric element 104 is set to 80 Hz. Electric element 104 is driven at a driving frequency equal to or higher than a minimum driving frequency of 17 Hz.

Shaft 110 includes main shaft portion 111, and eccentric shaft portion 112 eccentrically disposed at one end of main shaft portion 111 and integrally movable with main shaft portion 111. Rotor 103 is fixed to main shaft portion 111. Lubrication path 113 is provided within shaft 110 and in a surface of shaft 110. A lower portion of lubrication path 113 is extended to reach a predetermined depth of lubricant 106 for immersion in lubricant 106.

Cylinder block 114 includes cylinder 115 having a cylindrical shape (including a substantially cylindrical shape), and bearing portion 120. Bearing portion 120 supporting main shaft portion 111 of shaft 110 constitutes a cantilever bearing.

Piston 123 is reciprocatively inserted into cylinder 115. Valve plate 150 is attached to an end of cylinder 115. Cylinder 115 and piston 123 form compression chamber 116.

Piston pin 125 attached to piston 123 is positioned in parallel with eccentric shaft portion 112. As illustrated in FIGS. 4 and 5, seal portion 123 a and extension portion 123 b are formed on an outer circumferential surface of piston 123. Seal portion 123 a has a cylindrical sliding surface configured to produce a small clearance from an inner circumferential surface of cylinder 115. Extension portion 123 b has sliding surfaces disposed on both side surfaces of piston 123 in the rear of seal portion 123 a. Each sliding surface of extension portion 123 b has a radius same as a radius of seal portion 123 a, and is extended in an axial direction of piston 123 while maintaining a fixed width. Non-sliding portion 123 c is formed in each of vertically upper and lower surfaces of piston 123 in the rear of seal portion 123 a. Each of non-sliding portions 123 c has a larger clearance from the inner circumferential surface of cylinder 115, thereby constituting a portion not slidable.

As illustrated in FIG. 2, connecting rod 126 is composed of large-hole end portion 128, small-hole end portion 129, and rod portion 130. Large-hole end portion 128 engages with eccentric shaft portion 112. Small-hole end portion 129 connects with piston 123 via piston pin 125. Eccentric shaft portion 112 and piston 123 connect with each other via connecting rod 126 and piston pin 125.

In general, shaft 110, connecting rod 126, piston pin 125, and piston 123 constituting a part of compression element 105 are assembled such that shaft center 144 of main shaft portion 111 of shaft 110, and shaft center C of reciprocating piston 123 form an angle of π/2 (rad). A structure assembled in this manner achieves smoothest operation and reduces driving loss. Accordingly, this exemplary embodiment is constructed in a similar manner.

According to this exemplary embodiment, piston 123 is sized to have a diameter of 26 mm, a full length of 23 mm, and axial lengths of 8 mm and 15 mm for seal portion 123 a and extension portion 123 b, respectively. Each radius clearance between the inner circumferential surface of cylinder 115 and the sliding surface of seal portion 123 a, and between the inner circumferential surface of cylinder 115 and the sliding surface of extension portion 123 b is set to 0.005 mm. A radius clearance between the inner circumferential surface of cylinder 115 and non-sliding portion 123 c is set to 0.5 mm.

Considered herein is a projection surface extending in parallel with first center line 141 indicating a shaft center of bearing portion 120, and in parallel with second center line 142 indicating a shaft center of cylinder 115 as illustrated in FIG. 6. An angle formed by first center line 141 and second center line 142 is defined as angle a1. An absolute value of an angle of a tilt of shaft 110 with respect to bearing portion 120 produced by a diameter clearance between bearing portion 120 and main shaft portion 111 is defined as value c1 (rad). Cylinder block 114 (cylinder 115) is constructed such that angle a1 and value c1 satisfy the following equation (1).

a1=π/2+c1  (1)

Operation of the sealed compressor thus constructed is hereinafter described. When electric element 104 is turned on, rotor 103 causes rotation of shaft 110. Rotational movement of eccentric shaft portion 112 produced in accordance with rotation of shaft 110 is transmitted to piston 123 via connecting rod 126.

As a result, piston 123 starts reciprocating movement within cylinder 115. This reciprocating movement of piston 123 sucks refrigerant gas from a cooling system (not shown) having a freezing cycle, and supplies the refrigerant gas into compression chamber 116. The refrigerant gas is compressed in compression chamber 116, and again discharged to the cooling system.

Pumping operation produced by rotation of shaft 110 starts at a lower end of lubrication path 113. Lubricant 106 stored in the bottom of sealed container 101 passes through lubrication path 113, flows upward by the pumping operation, and horizontally scatters toward the entire circumference within sealed container 101. Scattered lubricant 106 reaches piston pin 125, piston 123 and the like to lubricate piston pin 125, piston 123 and the like.

Distortion of the piston is hereinafter described.

In a sealed compressor including a cantilever bearing structure, a compression load during compression of refrigerant gas is generally supported only on one side of main shaft portion 111 of shaft 110. In this case, shaft 110 is tilted within the diameter clearance between main shaft portion 111 and bearing portion 120 when a compression load is applied during a compression stroke as illustrated in FIG. 2. Accordingly, in the assembly setting π/2 (rad) for the angle of shaft center C of piston 123 with respect to shaft center 144 of main shaft portion 111, the valve plate 150 side of piston 123 is tilted upward from a horizontal line.

According to this exemplary embodiment, the valve plate 150 side of shaft center D of cylinder 115 is tilted beforehand in the upward direction from the horizontal line in consideration of the tilt of piston 123.

Accordingly, when a compression load is applied to piston 123 during the compression stroke, shaft center D of cylinder 115 is aligned with shaft center C of piston 123 as illustrated in FIG. 2. As a result, distortion of reciprocating piston 123 decreases.

As illustrated in FIG. 6, an intersection O is defined at an intersection of first center line 141 indicating the shaft center of bearing portion 120 and second center line 142 indicating the shaft center of cylinder 115. Absolute value c1 is defined as an absolute value of an angle of a tilt of shaft 110 with respect to bearing portion 120 produced by the diameter clearance between bearing portion 120 and main shaft portion 111. In this case, cylinder 115 is disposed such that angle a1 formed by first center line 141 indicating the shaft center of bearing portion 120 and second center line 142 indicating the shaft center of cylinder 115 satisfy equation (1).

More specifically, angle a1 expressed by equation (1) is determined as a design value of the angle of the shaft center of cylinder 115 according to this exemplary embodiment. Angle a1 is so designed as to approximate an actual value based on absolute value c1 of the angle of the tilt of shaft 110 with respect to bearing portion 120. Accordingly, distortion between piston 123 and cylinder 115 more securely decreases.

On the other hand, shaft 110 is tilted within the diameter clearance between main shaft portion 111 and bearing portion 120 when suction force is applied to piston 123 during the suction stroke as illustrated in FIG. 3. According to this exemplary embodiment, assembly is determined such that the angle of shaft center C of piston 123 with respect to shaft center 144 of main shaft portion 111 of shaft 110 becomes π/2 (rad) at the time of a tilt of shaft 110 within the diameter clearance of bearing portion 120. Accordingly, the valve plate 150 side of piston 123 is tilted downward from the horizontal line in this state. As a result, deviation is produced from shaft center D of cylinder 115 designed in consideration of the tilt of piston 123 during the compression stroke.

As apparent, shaft center C of piston 123 tilts and deviates downward from shaft center D of cylinder 115 when a suction load is applied to piston 123 during the suction stroke. In this case, a maximum tilt amount of seal portion 123 a in the radial direction produced at shaft center deviation angle α of piston 123 is expressed as (axial length L of seal portion 123 a)×sin (α) as illustrated in FIG. 5.

In a typical sealed compressor for use in applications similar to a use application of this exemplary embodiment, an axial full length of piston 123 is set to a length of seal portion 123 a to secure sealing and sliding reliability. The radius clearance of seal portion 123 a, i.e., 0.005 mm in this exemplary embodiment, is the minimum clearance in clearances produced by components of compression element 105. In this case, the maximum tilt amount of seal portion 123 a in the radial direction during the suction stroke becomes larger than 0.005 mm, the radius clearance of seal portion 123 a. Accordingly, distortion is produced between E part of piston 123 on the compression chamber 116 side, and F part of piston 123 on the eccentric shaft portion 112 side.

According to this exemplary embodiment, however, the sliding portion of piston 123 is composed of seal portion 123 a, and extension portion 123 b provided on both sides of piston 123 for supporting side pressure. In this case, F part corresponds to non-sliding portion 123 c having a radius clearance of 0.5 mm, which is sufficiently larger than 0.005 mm of the radius clearance of the seal portion. Accordingly, no contact is produced between F part of piston 123 and the inner circumferential surface of cylinder 115.

Moreover, the maximum tilt amount L×sin (α) of seal portion 123 a in the radial direction produced at shaft center deviation angle a becomes smaller than 0.005 mm of the radius clearance in the vicinity of E part as a result of small length L of seal portion 123 a.

In this case, distortion at E part of piston 123 decreases even when a suction load is applied during the suction stroke.

Accordingly, distortion between piston 123 and cylinder 115 decreases during the suction stroke, as well as during the compression stroke.

Furthermore, the suction force generated during the suction stroke is considerably smaller than the compression load, wherefore the tilt angle of piston 123 becomes smaller during the suction stroke than the compression stroke. Distortion between piston 123 and cylinder 115 also becomes smaller during the suction stroke than the compression stroke. Accordingly, distortion between piston 123 and cylinder 115 during the suction stroke effectively decreases.

According to this exemplary embodiment, therefore, efficiency improves by reduction of sliding loss produced between piston 123 and cylinder 115 during both the compression and suction strokes.

As described above, the sealed compressor according to this exemplary embodiment includes sealed container 101 that contains electric element 104, and compression element 105 driven by electric element 104. Compression element 105 includes shaft 110 that includes main shaft portion 111, and eccentric shaft portion 112 integrally movable with main shaft portion 111, and further includes bearing portion 120 that supports main shaft portion 111 of shaft 110 to constitute a cantilever bearing. Compression element 105 further includes cylinder 115 that compresses gas, piston 123 reciprocatively inserted into cylinder 115, and connecting rod 126 that connects eccentric shaft portion 112 with piston 123. Angle a1 formed by first center line 141 indicating a shaft center of bearing portion 120, and second center line 142 indicating a shaft center of cylinder 115, and absolute value c1 of an angle of a tilt of shaft 110 with respect to bearing portion 120 satisfy equation (1). An outer circumferential surface of piston 123 includes seal portion 123 a producing a clearance from an inner circumferential surface of cylinder 115, and forming a sliding surface, extension portion 123 b disposed in a rear of seal portion 123 a, and forming a sliding surface, and non-sliding portion 123 c disposed in the rear of seal portion 123 a, and not forming a sliding surface.

This structure reduces sliding loss of piston 123 and cylinder 115 during both the compression and suction strokes, thereby improving efficiency.

Extension portion 123 b has a radius same as a radius of seal portion 123 a, and forms the sliding surface that supports side pressure. This structure reduces local distortion of the piston, thereby preventing input increase and improving efficiency.

Electric element 104 is driven at a plurality of rotation speeds by an inverter circuit.

This structure prevents distortion of the piston within the cylinder even under a driving condition of low-speed rotation where a lubricant film thickness decreases on the sliding surface of the piston as a result of a small lubricant supply amount to the piston. This structure also prevents distortion of the piston within the cylinder during the suction stroke under a driving condition of high-speed rotation where the tilt of the piston increases due to a high compression ratio. Accordingly, efficiency improves.

Second Exemplary Embodiment

FIG. 7 is a schematic cross-sectional view of a refrigerator according to a second exemplary embodiment of the present invention. Described herein is a refrigerator presented as an example of a refrigeration device. The refrigerator illustrated in FIG. 7 includes the sealed compressor described in the first exemplary embodiment.

As illustrated in FIG. 7, heat insulating box 180 includes inner box 182, outer box 184, and heat insulating walls. Inner box 182 is produced by vacuum forming of a resin material such as ABS (Acrylonitrile Butadiene Styrene). Outer box 184 is made of a metal material such as pre-coated steel sheet. The heat insulating walls are produced by filling foamed heat insulating material 186 into a space defined by inner box 182 and outer box 184. Heat insulating material 186 is made of rigid urethane foam, phenol foam, styrene foam or the like. It is more preferable to use hydrocarbon cyclopentane for a foamed material in view of prevention of global warming.

Heat insulating box 180 is divided into a plurality of heat insulating sections. A revolving-type door is provided in an upper part, while drawer-type compartments are provided in lower part of heat insulating box 180. The plurality of heat insulating sections include refrigerating compartment 188, a pair of drawer-type switching compartment 190 and ice compartment 192 disposed side by side, drawer-type vegetable compartment 194, and drawer-type freezing compartment 196 in this order from above. A heat insulating door is attached to each of the respective heat insulating sections via a gasket. These doors are composed of refrigerating compartment revolving door 198, switching compartment drawer door 200, ice compartment drawer door 202, vegetable compartment drawer door 204, and freezing compartment drawer door 206 in this order from above.

Outer box 184 of heat insulating box 180 includes recessed portion 208 corresponding to a recessed rear part of a top surface of outer box 184.

In a freezing cycle, sealed compressor 210, a condenser (not shown) provided on a side or other portions of heat insulating box 180, capillary 212 corresponding to a decompressor, a drier (not shown) for removing moisture, evaporator 216, and suction piping 218 are connected in an annular shape. Sealed compressor 210 corresponds to the sealed compressor described in the first exemplary embodiment, and is elastically supported on recessed portion 208. Evaporator 216 is disposed in a rear of vegetable compartment 194 and freezing compartment 196. Cooling fan 214 is provided in the vicinity of evaporator 216.

Operation and effect of the refrigerator thus constructed are hereinafter described.

Initially, temperature setting and cooling system for the respective heat insulating sections are described.

A temperature of refrigerating compartment 188 is generally determined in a range from 1° C. to 5° C., with a lower limit set above a freezing temperature for refrigerating storage.

Temperature setting of switching compartment 190 is changeable by a user within a predetermined temperature zone, ranging from a freezing compartment temperature zone to a refrigerating compartment or vegetable compartment temperature zone.

Ice compartment 192 is an independent ice storage compartment. Ice compartment 192 includes a not-shown automatic ice making device to automatically produce ice and store the produced ice. A temperature of ice compartment 192 is set in the freezing temperature zone for storage of ice. However, the temperature of ice compartment 192 may be set at a freezing temperature in a range from −18° C. to −10° C. for storage of ice, which temperature is relatively higher than the freezing temperature zone.

A temperature of vegetable compartment 194 is often set at a temperature equivalent to the temperature range of refrigerating compartment 188, or at a temperature ranging from 2° C. to 7° C., which is slightly higher than the temperature range of refrigerating compartment 188. Freshness of leafy vegetables continues longer as the temperature of vegetable compartment 194 decreases toward a lower limit above a freezing temperature.

A temperature of freezing compartment 196 is generally set in a range from −22° C. to −18° C. for freezing storage. However, the temperature of freezing compartment 196 may be set in a low temperature range from −30° C. to −25° C. for improvement of a freezing storage state.

The respective compartments are sectioned by the heat insulating walls to efficiently maintain different temperature settings. However, heat insulating box 180 may be integrally formed by filling foamed heat insulating material 186 to reduce costs and improve heat insulation performance. Heat insulating box 180 formed by filling foamed heat insulating material 186 exhibits approximately twice the heat insulation performance of a structure formed of a heat insulating material such as styrene foam. Accordingly, heat insulating box 180 thus constructed is allowed to increase a storage volume by reduction of thicknesses of partitioning parts.

Operation of the freezing cycle is hereinafter described.

Cooling operation starts and stops in response to signals generated from a temperature sensor (not shown) and a control board based on the set temperatures within the refrigerator. Sealed compressor 210 performs predetermined compression operation in accordance with instructions of cooling operation. Discharged high-temperature and high-pressure refrigerant gas is condensed and liquefied at the condenser (not shown) while releasing heat, and decompressed by capillary 212 to become low-temperature and low-pressure liquid refrigerant. The generated liquid refrigerant reaches evaporator 216.

The refrigerant gas within evaporator 216 is evaporated and gasified by heat exchange with air inside the refrigerator in accordance with operation of cooling fan 214. Low-temperature cooling air after heat exchange is distributed by a damper (not shown) or the like to cool the respective compartments.

In sealed compressor 210 of the refrigerator performing the foregoing operation, cylinder block 114 includes bearing portion 120 and cylinder 115 disposed such that first center line 141 indicating the shaft center of bearing portion 120 and second center line 142 indicating the shaft center of cylinder 115 cross each other as described in the first exemplary embodiment. Angle a1 (rad) formed by first center line 141 and second center line 142, and absolute value c1 (rad) of the angle of the tilt of shaft 110 with respect to bearing portion 120 produced by the diameter clearance between bearing portion 120 and main shaft portion 111 satisfy equation (1). Piston 123 includes cylindrical seal portion 123 a constituting a sliding surface and producing a uniform clearance between an outer circumferential surface of piston 123 and an inner circumferential surface of cylinder 115. Piston 123 further includes extension portion 123 b disposed in the rear of seal portion 123 a, having a radius same as a radius of seal portion 123 a, and constituting a sliding surface for supporting side pressure.

In this structure, a sliding area in a tilted state of piston 123 decreases even when deviation between the shaft center of cylinder 115 and the shaft center of piston 123 increases during the suction stroke. This effect is produced by the configuration of piston 123 which includes extension portion 123 b constituting a sliding surface for supporting side pressure in the rear of cylindrical seal portion 123 a providing a sliding surface of piston 123, and eliminates a sliding surface in the vertical up-down direction.

This structure decreases local distortion of piston 123, thereby reducing sliding loss for improvement of efficiency of sealed compressor 210. As a result, reduction of power consumption of the refrigerator is achievable.

As described above, the refrigerator in this exemplary embodiment is a refrigeration device including the sealed compressor according to the first exemplary embodiment. Accordingly, the refrigeration device provided herein realizes reduction of power consumption.

INDUSTRIAL APPLICABILITY

As described above, the sealed compressor according to the present invention improves efficiency by reduction of sliding loss of a piston, and therefore is applicable not only to a household electric refrigerator, but also to a refrigeration device for an air conditioner, a vending machine, or various other apparatuses.

REFERENCE MARKS IN THE DRAWINGS

101 Sealed container

102 Stator

103 Rotor

104 Electric element

105 Compression element

106 Lubricant

110 Shaft

111 Main shaft portion

112 Eccentric shaft portion

113 Lubrication path

114 Cylinder block

115 Cylinder

116 Compression chamber

120 Bearing portion

123 Piston

123 a Seal portion

123 b Extension portion

123 c Non-sliding portion

125 Piston pin

126 Connecting rod

128 Large-hole end portion

129 Small-hole end portion

130 Rod portion

141 First center line

142 Second center line

144 Shaft center

150 Valve plate

180 Heat insulating box

182 Inner box

184 Outer box

186 Heat insulating material

188 Refrigerating compartment

190 Switching compartment

192 Ice compartment

194 Vegetable compartment

196 Freezing compartment

198 Refrigerating compartment revolving door

200 Switching compartment drawer door

202 Ice compartment drawer door

204 Vegetable compartment drawer door

206 Freezing compartment drawer door

208 Recessed portion

210 Sealed compressor

212 Capillary

214 Cooling fan

216 Evaporator

218 Suction piping 

1. A sealed compressor comprising a sealed container that contains an electric element, and a compression element driven by the electric element, wherein the compression element includes: a shaft that includes a main shaft portion, and an eccentric shaft portion integrally movable with the main shaft portion, a bearing portion that supports the main shaft portion of the shaft to constitute a cantilever bearing, a cylinder that compresses gas, a piston reciprocatively inserted into the cylinder, and a connecting rod that connects the eccentric shaft portion with the piston, an angle a1 formed by a first center line indicating a shaft center of the bearing portion, and a second center line indicating a shaft center of the cylinder, and an absolute value c1 of an angle of a tilt of the shaft with respect to the bearing portion satisfy equation (1): a1=π/2+c1  (1), and an outer circumferential surface of the piston includes: a seal portion producing a clearance from an inner circumferential surface of the cylinder, and forming a sliding surface, an extension portion disposed in a rear of the seal portion, and forming a sliding surface, and a non-sliding portion disposed in the rear of the seal portion, and not forming a sliding surface.
 2. The sealed compressor according to claim 1, wherein the extension portion has a radius same as a radius of the seal portion, and forms the sliding surface that supports side pressure.
 3. The sealed compressor according to claim 1, wherein the electric element is driven at a plurality of rotation speeds by an inverter circuit.
 4. A refrigeration device comprising the sealed compressor according to claim 1 in a freezing cycle. 